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Flores ‘hobbits’ were already small 700,000 years ago

The diminutive Homo floresiensis hominins, popularly referred to as the Flores hobbits, are thought to be descended from normally-sized hominins who underwent a phenomenon known as ‘insular dwarfism’ after they reached Flores. Food shortages combined with an absence of dangerous predators meant that smaller individuals, with lower calorific requirements, were at an advantage and over many generations the entire population ‘downsized’.

Up until now, the evidence for when this process begun have been tentative. The hominins originally found at the western Flores cave site at Liang Bua, though older than once thought, are still no more than 100,000 years old. It has been suggested that stone tools from the sites of Mata Menge and Wolo Sege in central Flores show technological continuity with artefacts associated with the original Homo floresiensis finds at limestone cave of Liang Bua in western Flores. The Mata Menge artefacts are 880,000 years old and those from Wolo Sege are at least at least a million years old, suggesting that hominins were on Flores by then, although these artefacts cannot tell us anything about the size of their makers. (Brumm, et al., 2006; Brumm, et al., 2010)

However, Mata Menge has now yielded actual hominin remains, which have been dated to 700,000 years ago by argon-argon and fission track methods. (Brumm, et al., 2016) They comprise an adult hominin fragmentary lower jawbone and six teeth. The fossils have been described as ‘Homo floresiensis-like’ and the jawbone and a molar teeth are even smaller than those of their Liang Bua counterparts. Thus Flores hominins were already downsized by this time. (Van den Bergh, et al., 2016)

References:

Brumm, A. et al., Age and context of the oldest known hominin fossils from Flores. Nature534, 249-254 (2016).